A user of a telecommunication network requests a service by dialing the number dedicated to the service. The call with this number is routed through the telecommunication network to a service switching exchange which recognize this call as call requesting the service. Then, this service switching exchange communicates via a data network with a service control facility, the so called service control point. This service control point contains a service logic which contains a description of the method that has to be executed to provide the service to the calling user. By a request of the service switching exchange the execution of this method by the service logic is initiated and the requested service is provided to the requesting user.
This service logic is realized as a single process handling all calls one after the other. Each of them going through a single queue. Each call is associated with a context allowing the state of the call not to be lost between user interaction. The service is executed through a finite state machine, taking as input the TCAP message as the context of the call.
The disadvantage of this architecture of provisioning services is that within the service control facility an incoming request for a service has to wait for execution until the current one has been processed out. Therefore, the rate of service requests that can be handled by the service control facility is strictly limited.